This invention relates to a manually or thermally operable overload protective circuit breaker comprising at least one pole,
a housing of electrically insulating material, having a central longitudinal axis and having in the housing a main switch chamber, PA1 an actuating element, preferably a pressure button or push-button, accessible from outside the housing and being arranged displaceably along the said central longitudinal axis, PA1 at least two contact posts associated with, and preferably inside the housing, PA1 an elbow lever lodged in the main switch chamber and comprising an actuating arm, a main contact arm and an elbow joint, each of the two arms having a first end at which the arms are articulatedly connected with each other by means of the said elbow joint, and a second arm end remote from the elbow joint; PA1 contact-making bridge means being responsively connected with the actuating element by means of the elbow lever, for making or breaking circuit between the two contact posts, PA1 restoring means, preferably a restoring spring, for permanently biassing the elbow lever toward a contact-breaking position; PA1 a first swivel joint articulatedly connecting the second arm end of the actuating arm of the elbow lever with the said actuating element, e.g. with the pressure button, PA1 a second swivel joint articulatedly connecting the second end of the main contact arm of the elbow joint with the contact making bridge means. PA1 an attachment casing mounted on the housing thereof, PA1 a signal contact lever comprising a fulcrum, a trip lever arm projecting from the fulcrum into the main switch chamber, and a signal contact arm extending into the said casing, PA1 a fixed contact and a signal contact spring which are both lodged in the casing and form a signal contact point therebetween, while PA1 the actuating arm of the elbow lever comprises tripping means, for instance of disk shape, which projects from the arm in the region of its first arm end, and which are adapted for engaging the signal contact lever when the elbow lever is in stretched position, and PA1 the signal contact arm is adapted for carrying out a swivel movement dependent on the position of the tripping means, and thereby acts upon the signal contact spring so as to make or break circuit with the fixed contact at the signal contact point. PA1 the intermediate U-portion of the signal contact spring is located in the casing on the same side, in axial direction, as the last-mentioned depth of the chamber, while PA1 a first one of the U-legs is arranged to extend adjacent the fixed contact, and preferably substantially parallel therewith, and is adapted to form the signal contact point with it. PA1 two metal sleeves having each a longitudinal sleeve axis, which axes enclose an acute angle whose apex points in a direction parallel with the central longitudinal housing axis and away from the contact posts in the housing; PA1 a first one of these sleeves being electrically conductively connected with the signal contact spring, and the other sleeve being connected in a like manner with the fixed contact. Preferably, the longitudinal sleeve axes define a plane which extends perpendicularly relative to the plane in which the signal contact lever can be swiveled. It is thereby possible possible to arrange the main circuit lines as well as the signal contact lines at the rear of the casing from the same side thereof, while the rearwardly opening, angular arrangement of the metal sleeves permits the electrical supply lines for the signal casing to be arranged without problems on both sides of the main lines and to be connected with their respective metal sleeves. PA1 The tripping means projecting outwardly from the actuating arm of the elbow lever extend in the same direction in which the elbow joint moves during folding together the arms of that lever. PA1 The contact posts are preferably located in the depth of the housing and the trip lever arm bears an abutment face, adapted for being engaged by the said tripping means, which is inclined in a direction toward the region of the housing containing the contact posts. PA1 This abutment face of the trip lever arm of the signal contact lever can also extend in a plane intersecting the central longitudinal axis of the housing at an angle of 45.degree. whose apex is located on the aforesaid axis and points toward the contact posts.
An overload protective circuit breaker of this type has been described in German Pat. No. 2,123,765. In this known construction, the elbow lever is movable between a substantially stretched, arrested limit position making circuit, and a maximally folded limit position breaking circuit. The centers of the swivel joints are located, in any position from the stretched to the maximally folded limit position of the elbow lever, on the central longitudinal axis which extends in the direction of the depth of the housing, i.e. toward the end thereof remote from the said actuating element.
In this known circuit breaker, the force of a spring adapted to act upon the elbow lever urges the actuating arm of the elbow lever away from its main contact arm. When the circuit-making position is attained, the elbow lever is arrested by a catch which can be released by hand, or by thermal action. The construction of this known circuit breaker, which has been described more in detail in the above-mentioned German Pat. No. 2,123,765, permits obtainment of an instant making of the circuit by simple, space-saving means, and, moreover, a manual release, an extremely rapid thermal release and a trip-free release and breaking of the circuit.
A simlar construction of an elbow lever and associated auxiliary levers has been described in German patent No. 2,507,454. In this case, the single pole overload protective circuit breaker constitutes a multi-pole switch and comprises auxiliary levers being connected via a common shaft, an arrangement which permits obtainment of an essentially simultaneous release of all poles without requiring any greater mechanical forces influencing the switching time than would be required in the case of a single pole release.
A drawback of conventional overload protective circuit breakers, regardless whether they have a single pole or plurality of poles, resides in the lack of a signal contact point which will, by means of a signal circuit connected therewith, yield information about the momentary state of the circuit breaker. For example, a switch box having a number of protective circuit breakers in the power supply, e.g., of an electric air-craft wiring, can be compared herewith, in which the lack of signal lamps indicating the release of a circuit breaker would make it most difficult to locate a point of failure quickly and accurately.
An overload circuit breaker having a signal contact point has been described in Swiss Pat. No. 233,959 in which a contact bridge displaces, during its closing movement, a dividing wall of insulating material which projects into the path of shifting movement of the contact bridge, such displacement occurring in contact-making direction. The free end of this dividing wall, on the side of the signal contact, controls a movable auxiliary contact member of the signal contact point. A drawback of this construction resides in the fact that the restoring force of an auxiliary contact spring acts directly counter to the closing direction of the contact bridge. This reduces the attainable contact pressure and, together therewith, the current-carrying capacity of the main contact. Moreover, the restoring force increases friction between the individual parts at the latching-in point of the elbow lever whereby the required releasing force is increased in turn. This prolongs the release time of conventional overload circuit breakers of this kind, and naturally reduces their protective effectiveness.